Jan Klos

EQA of immunohistochemical markers of genitourinary tract – NordiQC experience

The results of 28 EQA assessments of 14 selected immunohistochemical markers with 9 to 284 participating laboratories each are presented and analyzed.

The assessment of prostate markers showed high to average pass rate (PSA 89%, PAP 88%, Prostein/P501S 73%, NKX3.1 65% and AMACR/P504S 89%) and a number of different antibodies available in concentrated form as well as RTU products capable of producing the optimal results. Markers like P63 and ΔNp63 (P40), important among other for detection of basal/myoepithelial cells as well as squamous and urothelial differentiation, showed high pass rate for P63 (89%) and average pass rate for P40 (74%) with several Abs giving optimal results. The results of staining for High Molecular Weight Cytokeratins confirmed that the number of products mostly directed towards CK5, CK5/6 can produce optimal results. The common use of the clone 34βE12 (reacting with CKs 1, 5, 10 and 14 and called Cytokeratin High Molecular Weight) as a primary antibody has contributed however to significantly lower than average pass rate (45%). The cross-reactivity with the other epitope (probably degenerated CK19) in the same cellular compartment was observed when this clone was used with HIER and sensitive protocol settings. This cross-reactivity could be reduced, but not completely eliminated, with proteolytic pre-treatment or a combined pre-treatment with both HIER and proteolysis. The risk of false positive interpretation was judged high as the consequence of this cross-reactivity. The clone 34BE12 was considered inappropriate as a general marker for High Molecular Weight Cytokeratins however it still may do for demonstration of basal cells in the prostate. Two assessments of PAX8 (pass rate 71%) demonstrated that a number of Abs is capable of producing optimal results. It also showed that the recommended protocol for commonly used rmAB MRQ-50 on Ventana platform may need modification. One assessment of PAX2 involving 9 participants using 3 concentrated Abs and 2 RTU products produced no optimal results. Optimal results for GATA3 (pass rate 72%) were seen only with mAb L50-823 for both concentrated and RTU forms. Regarding PLAP and SALL4, both have shown very high pass rate (91% and 98% respectively) with a good choice of antibodies for PLAP and the only one highly successful clone for SALL4. Two assessments of OCT3/4 (pass rate 77%) have identified a number of Abs giving optimal results.  Some cross-reactivity with different cell types was observed with mAbs MRQ-10 and C-10. The results have indicated also that recommended protocol for Ventana platform with mAb C-10 may need modification.                                                                                                                                                    Summary: The analysis of the results gave an important information regarding quality of used products, performance level of applied Abs on different platforms and technical parameters important for optimal results. The higher rate of optimal results with RTU products than with concentrated Abs for a number of antibodies may indicate the way for future improvements of the staining quality.

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Dr. Jan Klos M.D. is a Senior Consultant and a Head of the Immunohistochemistry Section in the Department of Pathology, Stavanger University Hospital, Norway.  He was educated at Medical University of Warsaw (1968-1974), trained and practiced pathology in Warsaw, Poland (1975-1982). Since 1982 he has been practicing and teaching pathology abroad, working first at the University of Jos, Nigeria (1982-84), later at the Central Hospitals in Falun and Gavle as well as at University of Umeå, Sweden (1984-1998), and since 1998 in Stavanger, Norway. His professional interest is diagnostic pathology with the main focus on haematopathology, pathology of the breast and cytopathology. He is a co-author of more than 40 publications in pathology. He is also a member of Editorial Board of Polish Journal of Pathology. Since 2009 he is a member of the core group in NordiQC, representing there also Norwegian Society of Pathologists, and 2015-16 he was appointed as a Chairman of NordiQC. He has been actively involved in teaching immunohistochemistry since 2000 as an invited lecturer on various international and national courses and meetings. During 2008-2013 he was also a co-organizer of annual NordiQC Workshops in Immunohistochemistry and from 2014 he is an organizer of the annual NordiQC Academy courses “Immunohistochemistry for Pathologists”.